Effects of Giant Burreed (Sparganium eurycarpum) and Shade on Wild Rice (Zizania palustris)

Abstract

Studies were conducted at Grand Rapids, MN, to determine the effect of giant burreed (Sparganium eurycarpumEngelm. # SPGEU) planted at 6, 12, and 24 corms/m2on wild rice (Zizania palustrisL. ‘K2′) growth and yield. Giant burreed, a spreading perennial, had shoot densities of 21, 29, and 42/m2at harvest for the 6, 12, and 24 corms/m2treatments, respectively. Wild rice yield and panicle number were reduced approximately 60% when giant burreed shoot density was 40/m2or higher when compared to the weed-free control. Giant burreed did not interfere with nutrient uptake of wild rice on a whole-plant basis, and increased N fertilizer application did not reduce losses in dry weight. Giant burreed reduced penetration of photosynthetically active radiation (PAR) from 2 to 35% in the wild rice canopy from the early tillering to the anthesis stage of wild rice development. In growth chamber studies, wild rice dry weight and panicle number were reduced by 46 and 65%, respectively, when wild rice was shaded for 12 weeks and compared to a full light treatment. Reduction of PAR penetration into the wild rice canopy appears to be the major mechanism of giant burreed interference with wild rice.